From 5d69a524f81f234b3fbc41d49ba18d6f6886baba Mon Sep 17 00:00:00 2001 From: jcorgan Date: Thu, 3 Aug 2006 04:51:51 +0000 Subject: Houston, we have a trunk. git-svn-id: http://gnuradio.org/svn/gnuradio/trunk@3122 221aa14e-8319-0410-a670-987f0aec2ac5 --- docs/exploring-gnuradio/fm_demod_example.xml | 123 +++++++++++++++++++++++++++ 1 file changed, 123 insertions(+) create mode 100644 docs/exploring-gnuradio/fm_demod_example.xml (limited to 'docs/exploring-gnuradio/fm_demod_example.xml') diff --git a/docs/exploring-gnuradio/fm_demod_example.xml b/docs/exploring-gnuradio/fm_demod_example.xml new file mode 100644 index 000000000..3036f88ba --- /dev/null +++ b/docs/exploring-gnuradio/fm_demod_example.xml @@ -0,0 +1,123 @@ + +Broadcast FM Receiver + +#!/usr/bin/env python + +from gnuradio import gr +from gnuradio import audio +from gnuradio import mc4020 +import sys + +def high_speed_adc (fg, input_rate): + # return gr.file_source (gr.sizeof_short, "dummy.dat", False) + return mc4020.source (input_rate, mc4020.MCC_CH3_EN | mc4020.MCC_ALL_1V) + +# +# return a gr.flow_graph +# +def build_graph (freq1, freq2): + input_rate = 20e6 + cfir_decimation = 125 + audio_decimation = 5 + + quad_rate = input_rate / cfir_decimation + audio_rate = quad_rate / audio_decimation + + fg = gr.flow_graph () + + # use high speed ADC as input source + src = high_speed_adc (fg, input_rate) + + # compute FIR filter taps for channel selection + channel_coeffs = \ + gr.firdes.low_pass (1.0, # gain + input_rate, # sampling rate + 250e3, # low pass cutoff freq + 8*100e3, # width of trans. band + gr.firdes.WIN_HAMMING) + + # input: short; output: complex + chan_filter1 = \ + gr.freq_xlating_fir_filter_scf (cfir_decimation, + channel_coeffs, + freq1, # 1st station freq + input_rate) + + (head1, tail1) = build_pipeline (fg, quad_rate, audio_decimation) + + # sound card as final sink + audio_sink = audio.sink (int (audio_rate)) + + # now wire it all together + fg.connect (src, chan_filter1) + fg.connect (chan_filter1, head1) + fg.connect (tail1, (audio_sink, 0)) + + return fg + +def build_pipeline (fg, quad_rate, audio_decimation): + '''Given a flow_graph, fg, construct a pipeline + for demodulating a broadcast FM signal. The + input is the downconverted complex baseband + signal. The output is the demodulated audio. + + build_pipeline returns a two element tuple + containing the input and output endpoints. + ''' + fm_demod_gain = 2200.0/32768.0 + audio_rate = quad_rate / audio_decimation + volume = 1.0 + + # input: complex; output: float + fm_demod = gr.quadrature_demod_cf (volume*fm_demod_gain) + + # compute FIR filter taps for audio filter + width_of_transition_band = audio_rate / 32 + audio_coeffs = gr.firdes.low_pass (1.0, # gain + quad_rate, # sampling rate + audio_rate/2 - width_of_transition_band, + width_of_transition_band, + gr.firdes.WIN_HAMMING) + + # input: float; output: float + audio_filter = gr.fir_filter_fff (audio_decimation, audio_coeffs) + + fg.connect (fm_demod, audio_filter) + return ((fm_demod, 0), (audio_filter, 0)) + + +def main (args): + nargs = len (args) + if nargs == 1: + # get station frequency from command line + freq1 = float (args[0]) * 1e6 + else: + sys.stderr.write ('usage: fm_demod freq\n') + sys.exit (1) + + # connect to RF front end + rf_front_end = gr.microtune_4937_eval_board () + if not rf_front_end.board_present_p (): + raise IOError, 'RF front end not found' + + # set front end gain + rf_front_end.set_AGC (300) + + # determine the front end's "Intermediate Frequency" + IF_freq = rf_front_end.get_output_freq () # 5.75e6 + + # Tell the front end to tune to freq1. + # I.e., freq1 is translated down to the IF frequency + rf_front_end.set_RF_freq (freq1) + + # build the flow graph + fg = build_graph (IF_freq, None) + + fg.start () # fork thread(s) and return + raw_input ('Press Enter to quit: ') + fg.stop () + +if __name__ == '__main__': + main (sys.argv[1:]) + + -- cgit From f919f9dcbb54a08e6e26d6c229ce92fb784fa1b2 Mon Sep 17 00:00:00 2001 From: Tom Rondeau Date: Fri, 13 Apr 2012 18:36:53 -0400 Subject: Removed whitespace and added dtools/bin/remove-whitespace as a tool to do this in the future. The sed script was provided by Moritz Fischer. --- docs/exploring-gnuradio/fm_demod_example.xml | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) (limited to 'docs/exploring-gnuradio/fm_demod_example.xml') diff --git a/docs/exploring-gnuradio/fm_demod_example.xml b/docs/exploring-gnuradio/fm_demod_example.xml index 3036f88ba..b417da0a8 100644 --- a/docs/exploring-gnuradio/fm_demod_example.xml +++ b/docs/exploring-gnuradio/fm_demod_example.xml @@ -24,10 +24,10 @@ def build_graph (freq1, freq2): audio_rate = quad_rate / audio_decimation fg = gr.flow_graph () - + # use high speed ADC as input source src = high_speed_adc (fg, input_rate) - + # compute FIR filter taps for channel selection channel_coeffs = \ gr.firdes.low_pass (1.0, # gain @@ -42,9 +42,9 @@ def build_graph (freq1, freq2): channel_coeffs, freq1, # 1st station freq input_rate) - + (head1, tail1) = build_pipeline (fg, quad_rate, audio_decimation) - + # sound card as final sink audio_sink = audio.sink (int (audio_rate)) @@ -84,7 +84,7 @@ def build_pipeline (fg, quad_rate, audio_decimation): fg.connect (fm_demod, audio_filter) return ((fm_demod, 0), (audio_filter, 0)) - + def main (args): nargs = len (args) @@ -106,13 +106,13 @@ def main (args): # determine the front end's "Intermediate Frequency" IF_freq = rf_front_end.get_output_freq () # 5.75e6 - # Tell the front end to tune to freq1. + # Tell the front end to tune to freq1. # I.e., freq1 is translated down to the IF frequency rf_front_end.set_RF_freq (freq1) # build the flow graph fg = build_graph (IF_freq, None) - + fg.start () # fork thread(s) and return raw_input ('Press Enter to quit: ') fg.stop () -- cgit